Added in stdlib as per #2014. (#2017)

(cherry picked from commit 9b70aec31de3d7c179fc8425d7af7babd96be2c5)

src/renderer.c

@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <assert.h>
 #include <math.h>
 #include <ft2build.h>